ᐅ Ventilation System with Heat Recovery – Sensible or Not?

But the supply air was not warmed by the exhaust air, but by the thermal energy from the window, which you provide by heating the room. In contrast, a heat recovery system uses the energy from the exhaust air that would otherwise be wasted.

Of course, I know this rumor as well: "Ytong® soaks up water." Try putting a aerated concrete block and a perforated brick in a tub of water overnight; you will probably be very surprised. It’s similar to the equally persistent rumor: [I]"Meat dissolves in Coca Cola®"[/I]

I rather imagine it like this, construction expert:

I would submerge a perforated brick and an aerated concrete block in water for weeks or months... then leave both in the sun for a day.
The perforated brick will be dry afterward, while the aerated concrete block still holds some residual moisture because it doesn’t release it as well...

I am not talking about problems with moisture entering aerated concrete during normal living conditions, but rather that it takes a bit longer for the initial construction moisture to leave the block.

Also, expanded polystyrene (EPS) is not designed for use in standing water because over time the “beads” fill with water and the insulation effect is lost… but if I put EPS in water overnight, I still don’t notice any effects…

But the supply air was not warmed by the exhaust air, rather by the heat energy from the window, which you provide by heating the room. Heat recovery, on the other hand, uses the energy in the exhaust air that would otherwise be lost.

I am aware of that.
However, since most people already understand that a central, controlled mechanical ventilation system with heat recovery is not economically feasible, the only remaining benefits are moisture control and comfort.

Moisture protection is also provided by a decentralized exhaust system, and comfort is not nearly as compromised as is often claimed. It’s not like opening a window when it’s -5°C (23°F) outside…

Regarding moisture and aerated concrete, I read something interesting about this topic from Ytong.

It states that Ytong becomes fully saturated after 2-3 days in water and that it then takes 2-4 weeks for the moisture to decrease to a level comparable to the moisture exposure in a new building...

That’s all on this topic....

Now, comparable information for other "bricks" is missing. That’s all on that.

Hello,

Shism schrieb:
I wonder provocatively whether your experiences might be related to the fact that you mainly build with aerated concrete? I have often heard that aerated concrete retains more moisture during the construction phase and does not dry as quickly. Therefore, the requirements for the occupants' ventilation behavior are particularly strict during the first 1-2 years...

I wanted to add a few words to my answer to you without technical jargon, but pressed the wrong button and lost it; that can happen... so here we go again, without technical jargon.

I don't find your question provocative.

As I often write, there is no “ultimate” masonry material; each has its pros and cons. For example, masonry made of fired bricks will generally shrink and creep, especially walls built with thin-bed mortar. Sand-lime brick does not even come close in terms of good thermal insulation properties. Aerated concrete, due to its fine pore structure, is highly capillary-active, meaning that when water comes into contact with an element made of aerated concrete, the material absorbs moisture—albeit delayed—but overall it can store relatively large quantities of water within its structure.

Therefore, careful handling of this material is especially important, and during the shell construction phase, an adequate protection against penetrating rain must be ensured at all exposed surfaces made of aerated concrete.

However, the advantages of this building material cannot be denied.

• Wide variety of sizes: Aerated concrete can be produced in many different dimensions—from standard blocks to large reinforced panels
• Excellent thermal insulation: Aerated concrete has a very low thermal conductivity, resulting in high thermal efficiency. This means significant potential savings in heating and cooling costs
• Extremely lightweight: Aerated concrete weighs about 50% less than comparable materials
• High compressive strength: Aerated concrete is a solid product and extremely load-bearing. The entire surface is included in structural engineering calculations
• High dimensional accuracy: Thanks to its precision, aerated concrete is very easy to process, as thick mortar layers are unnecessary
• High sound insulation: The porous structure of aerated concrete provides good soundproofing
• High fire resistance: Aerated concrete offers extremely high fire resistance of at least 4 hours or more
• Termite resistant: Aerated concrete is not susceptible to damage from termites or other insects
• Good workability: Due to the excellent size-to-weight ratio, building with aerated concrete is very fast
• Recognized as an ecological building material

Even though aerated concrete is less effective in sound insulation compared to sand-lime brick, this is negligible nowadays with external masonry thicknesses of 36.5cm (14 inches) and above.

Recently, we have also worked extensively with hollow clay blocks. Aside from the fact that careful processing of the material is important for other reasons, I have also found here that ventilation is simply essential—especially when an external thermal insulation composite system (ETICS) or external insulation finish system (EIFS) has been applied; which—likely completing the circle—applies equally to all other masonry materials.

Regards, Bauexperte

Hello,

Shism schrieb:
I imagine it more like this, Bauexperte:

I soak a hollow brick and an aerated concrete block in water for weeks or months... then I leave both in the sun for a day.. The hollow brick is dry afterwards, while the aerated concrete block still retains some moisture because it does not release it as easily...

I would agree with that.

Regards, Bauexperte